I would too! I've already setup custom pages for the 4xx and 5xx series that are more common; 401, 403, 404 and 500s. Those 500s are mandatory! And so are the 404s. I'm also finding that it is interesting to watch the other 4xx errors that may be generated.
I've been following that fellow who goes by the name of IncrediBILL and listening to his Rants about Bad Bots and such. I do believe that guy is on to something and we've started to lock down our Windows Servers in response to increased probing, etc.
I've definitely noticed something since setting up the custom pages, the actual error counts are way down from what they normally are. I do believe that our Stern warnings and well thought out error pages are a deterrent in some instances. I know there are humans generating those errors in advance of letting loose their pesky little bots. If we can get them in advance, be proactive, then we don't have to chase the little buggers after the fact.
I really wish I would have stayed away from that IncrediBILL character, what a time suck this Bad Bot Business is! We've got a lineup of Enterprise solutions in the works and so does he for the *nix side of things.
I'm a man of me word. Last year I started a topic stating that we were going to be banning 75% of the planet in 2009 and moving forward. Well, we've started that process and will be slowly rolling it out across all of the servers under our control.
Ban 75% of the Planet